Regenerative heat exchanger&#39;s plate heat transfer surface details



March 14, 1967 A. J. GRAM, JR.

REGENERATIVE HEAT EXCHANGERS PLATE HEAT TRANSFER SURFACE DETAILS 2Sheets-Sheet 1 Filed Aug. 30, 1965 INVENTORS Arrhur J. Gram,Jr

Andrew P. Lecon Ai'ToRNEY A. J. GRAM, JR, ETAL. 3,308,876 REGENERATIVEHEAT EXCHANGERS PLATE HEAT TRANSFER SURFACE DETAILS March 14, 1967 FiledAug. 30, 1965 2 Sheets-Sheet 2 FIG.3

FIG.4

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n m 8 Y m -L E Y N N R E. O VJW T N e .l r n TA r A Y B U v v UnitedStates Patent 3,308,876 REGENERATIVE HEAT EXCHANGERS PLATE HEAT TRANSFERSURFACE DETAILS Arthur J. Gram, Jr., Wadsworth, and Andrew P. Lecon,

Akron, Ohio, assignors to The Babcock & Wilcox Company, New York, N.Y.,a corporation of New Jersey Filed Aug. 30, 1965, Ser. No. 433,620Claims. (Cl. 16510) The present invention relates to regenerative heatexchangers, and more particularly to an improved construction of closelyspaced heat exchange elements for rotary regenerative heat exchangers.

Rotary regenerative air heaters are well known wherein heat exchangeelements are arranged in sector shaped compartments within a cylindricaldrum where a heating fluid and a fluid to be heated are passed incountercurrent relationship through separate compartments containing theheat exchange elements. Ordinarily the heat exchange elements are formedof parallel plates spaced for turbulent flow therethrough of the heatingfluid and the fluid to be heated. It is also known to utilize variousforms of spacers to establish the desired spacing between the parallelplates of the heat exchange elements. When using turbulent flowconditions for the fluid passing through the heat exchanger it isfrequently desirable to arrange the heat exchange elements so as topermit limited vibration of plates during cleaning or soot blowingperiods to aid in cleaning the heat exchange surfaces of the elements.

It has been found that heat exchange elements formed of closely spacedparallel plates are highly effective for heat exchange purposes wherethe fluid flow velocity through the heat exchange elements is of anon-turbulent or laminar flow characteristic. In such heat exchangersthe depth of the heating surfaces can be substantially less than thedepth of surface in turbulent flow heaters with equal heat exchangeefliciency.

It has been found that it is essential to assemble the heat exchangesurfaces of a non-turbulent or laminar flow heater so as to maintain thedesired plate spacing under all operating conditions. This has beenaccomplished in accordance with the present invention by use of a rigidstructure which reinforces the assembly of heat exchange elements tomaintain the desired spacing and the desired fluid flow characteristicsthrough the heat exchange elements during operation. More specificallythe invention involves the construction of heat exchanger elements wherethe plates are stamped from a continuous strip of metal to form aselected pattern of perforations and indentations. The strip is bentalong the perforations with the remaining metal providing hinges and theindentations providing a definite spacing when the plates are compacted.The length of the assembled package of heat exchange elements isdependent upon the number of plates in the assembly. The assembledpackage of spaced heat exchan e plates is attached to an elementpositioned along the top and bottom of the plates and welded to theedges thereof to form a rigid-and rugged package which will establishand maintain the desired fluid flow area between the heat exchangeplates.

The various features of novelty which characterize our invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which we have illustrated and described a preferred embodimentof the invention.

3,308,876 Patented Mar. 14, 1967 0f the drawings:

FIG. 1 is an isometric view, partly in section, of a regenerative heatexchanger containing heat exchange elements constructed and arrangedaccording to the present invention;

FIG. 2 is an enlarged isometric view of heat exchange elementsconstructed and arranged according to the invention;

FIG. 3 is an elevation view of the heat exchange plates shown in FIG. 2;

FIG. 4 is a plan view of the heat exchange plates shown in FIG. 2;

FIG. 5 is a schematic illustration of a die arrangement formanufacturing the heat exchange plates; and

FIG. 6 is an enlarged plan of the heat exchange plates as produced inthe die shown in FIG. 5.

The rotary regenerative heater illustrated in FIG. 1 includes astationary housing 10 arranged for the separate introduction anddischarge of a heating fluid and a fluid to be heated. A cylindricalrotor 11 is mounted for rotation about a horizontal axis within thehousing 10 and is constructed with radial partitions 12 extendingsubstantially the full axial or longitudinal length of the rotor 11. Thepartitions 12 separate the cylindrical rotor into a plurality of sectorswhich are provided with heat transfer elements constructed in accordancewith the present invention and arranged in axially spaced disk-likemasses 13 adjacent the opposite ends of the rotor. Suitable seals, suchas disclosed in copending application S.N. 249,736, are mounted on thehousing to cooperate with the rotor in directing separate countercurrentfluid flows through the housing and the sectors of the cylindricalrotor. As the rotor is rotated about a shaft 14, the sectors of heattransfer material are alternately heated by contact with the heatingfluid and then cooled by contact with the fluid to be heated.

As shown specifically in FIG. 1, the housing 10 is provided with anupper heating fluid inlet 15 radially arranged relative to the rotor sothat the incoming fluid enters the axial mid-portion of the flowcompartments formed between adjacent partitions 12 of the rotor, dividesas it turns to flow through the disk-like masses 13 of heat transfermaterial positioned adjacent the opposite ends of the rotor 11, anddischarges upwardly through radial outlet ducts 16 positioned in thehousing 10 outwardly adjacent the opposite ends of the rotor 11. Theflow of heating fluid is illustrated by the arrows 17.

Radial inlets 20 are provided in the opposite ends of the lower portionof the housing 10, for the admission of the fluid to be heated. Theincoming fluid flows axially of the rotor through the disk-like masses13 to combine in the mid-portion of the rotor and to discharge radiallythrough an outlet 21 formed in the lower portion of the housing 10. Thedirection of flow of the fluid to be heated is illustrated by the arrows22.

In a regenerative heater of the type disclosed, the depth of thedisk-like mass 13 of heat transfer material positioned in the sectors isadvantageously minimal in the direction of gas flow, i.e. longitudinallyor axially of the shaft 14, and may be of the order of 6 to 16 inches,for example, to meet heat exchange requirements in the usualinstallation. The thickness of the mass 13 may be divided into two ormore layers of elements for ease of installation and removal. Forexample, the cold end of the heat exchange mass, i.e. the outermostlayer, may be only 2 or 3 inches in depth and may be constructed of lowalloy metal to resist corrosion. The remaining layer or layers of heatexchange elements may be constructed of carbon steel, for example, 2 to6 inches in thickness.

3 Each layer may be assembled of a plurality of packaged elementspositioned in side by side and end to end relationship and assembled asa pie shaped mass to fit in the sector formed between adjacentpartitions 12.

When installed in the rotor 11 the sector shaped layers may be spaced inthe direction of gas flow to provide a clearance for separate insertionor removal of each layer and to provide a mixing and distribution effectfor the fluids passing through one layer into another layer of heatexchange surfaces. The space between layers may be of the order of Ainch.

The heat exchange elements forming the masses .13 are constructed andarranged to provide closely spaced surfaces between which the fluidsflow. As shown in Fig. 6 a strip of steel 30, having the desiredthickness and width, is passed between upper and lower dies 31 and 32respectively, where the strip is formed to the desired configuration.The width of the strip 30 corresponds to the depth (in the direction offluid flow) of the layer of heat exchange surface installed in theregenerative heater. For example, the width of the strip may be 2 to 6inches and the thickness may be 26 gage (0.0179 inch).

The dies 31 and 32 are vertically relatively movable by the usualstamping mechanism (not shown) to perforate and emboss the striptherebetween in a pattern such as shown in FIG. 6, for example. Asshown, the strip is perforated to form slotted openings 33 of, forexample, 0.045 inch in the longitudinal dimension of the strip, and inchin the transverse direction and so spaced as to leave metal connectingadjoining portions A and B of. the strip. The connecting metal 36provides hinges so that the strip may be bent at the hinges to formparallel plate surfaces corresponding to the portions A and B.

When the strip is perforated or cut to form the portions A and B eachportion is simultaneously deformed or embossed to form dimples 37. Asshown, in FIGS. and 6 the dimples 37 formed in portion A are displaceddownwardly from the plane of the strip while the dimples in portion Bare oppositely, or upwardly, displaced. The dimples may be of the orderof Ms inch diameter and extend 0.045 inch beyond the plane of the stripportion A or B so as to establish a plate spacing of 0.045 inch betweensurfaces of the heat exchange mass when the elements are assembled forthe flow of fluid therethrough. The spacing between dimples is arrangedto maintain the interplate spacing with a minimum of fluid flowrestriction between the plates. In a typical arrangement the dimples aretransversely spaced /2 inch while the longitudinal spacing may beapproximately 1 inch.

As shown oin FIGS. 3, 4, 5 and 6 the dimples 37 may be arranged inportions A and B to a common longitudinal spacing, as each is measuredfrom a corresponding maintained by welding transverse metal elements,such as rods or strips 46 and 48 in edge relationship with the plates 40to 45 on opposite sides of the package. The strips 46 and 47 arepositioned between the metal hinges 36 and not only rigidly hold theplate to plate relationship of the package, but also provide structuralstrength to the assembly.

In the embodiment shown the width of the strip 30, and thus the depth ina fluid flow direction of the package 38 is 2 inches while the height ofeach package is 3 /2 inches. When a package is formed 4 to 6 inches indepth, more than one of the strips 46 and 47 are welded between hingesto the edges of the plates to increase the rigidity of the package.

While in accordance with the provisions of the statutes we haveillustrated and described herein the best form and mode of operation ofthe invention now known to us, those skilled in the art will understandthat changes may be made in the form of the apparatus disclosed withoutdeparting from the spirit of the invention covered by our claims, andthat certain features of our invention may sometimes be used toadvantage without a corresponding hinge end. The transverse spacing inportion B will be displaced with respect to the transverse spacing inportion A so that a dimple in one portion will not correspond intransverse location with the dimple in an adjoining portion. a

With two portions A and B of the strip 30 formed simultaneously, thestrip is advanced a distance equal to the length. of portions A and Bafter each action of the die press. After leaving the dies 31 and 32,the successive portions A and B are folded in alternate directions atthe hinges to form a package of parallel spaced plates. The bending ofthe successive portions A and B may be performed manually ormechanically and the number of plates so arranged will be dependent onthe length of the package of heat exchange elements desired.

As illustrated in FIGS. 3, 4 and 5 a portion of a package 38 of heatexchange elements is formed by arranging successive bent portions A andB in abutting relationship.

As shown the plates 40, 42 and 44 correspond with the plates B while theplates 41, 43 and correspond with the plates A. The dimples 37B ofplates 40, 42 and 44 bear against the adjoining surfaces of the plates41, 43 and 45 to establish the spacing therebetween which is use ofother features.

What is claimed is:

1. In a rotary regenerative fluid heater having a stationary housing, acylindrical rot-or having radial partitions forming a plurality ofsector shaped compartments therein, regenerative heat exchange materialpositioned in each of said compartments, means for passing a heatingfluid and a fluid to be heated in counterflow relationship separatelythrough said compartments containing said regenerative heat exchangematerial, said regenerative heat exchange material comprising aplurality of rows of metallic plates arranged in stacked rows, theplates in each row being connected by a perforate 'hinge at oppositeends with an opposite adjacent plate, each plate being dimpled in thesame assembled direction to provide a closely spaced fluid flowpassageway between adjacent.

plates, and metallic means transversely positioned along and betweenopposite connected ends of and welded to each of said plates for rigidlyattaching said plates in each row of plates to maintain said closelyspaced relationship therebetween.

2. A heat exchange package adapted for rotors in a regenerative heatercomprising a plurality of closely spaced parallel plates formed from acontinuous strip of metal, said strip being perforated at longitudinallyequally spaced transverse locations and bent in opposite directions atthe perforations to form the connecting end portions of said parallelplates, means for substantially uniformly spacing said plates, and meansfor maintaining in said package the spaced relation of said parallelplates including a metal element extending transversely along andbetween the connecting end portions of said plates,

said element being welded to the edge of each of said plates.

3. A heat exchange package adapted for rotors in a regenerative heatercomprising a plurality of closely spaced substantially parallel plates,each plate connected by a perforate hinge portion at opposite ends withan opposite adjacent plate, each plate having spaced portions thereofdisplaced in one direction, said displaced portions providing asubstantially uniform spacing between said plates when the displacedportions of one plate contact the surface of a next adjacent plate, anda metal element extending transversely along and between the connectedends of said plates and engaged with the edges of said plates to rigidlyhold the plates in said package.

4. A heat exchange package adapted for rotors in a laminar flowregenerative fluid heater comprising a plurality of flat plates, eachplate integrally connected by a perforate hinge at opposite ends with anopposite adjacent plate, each plate being dimpled in one direction, saiddimples providing a substantially uniform transverse spacing betweensaid plates when the dimples of one plate contact the flat surface of anext adjacent plate, and a metal element extending the length of saidpackage adjacent opposite connected ends between the integralconnections thereof and welded to the edges of said plates to rigidlyconnect the plates in each package.

5. A heat exchange package adapted for rotors in a laminar flowregenerative fluid heater comprising a plurality of substantiallyuniformly spaced parallel plates, each plate connected by a perforatehinge at opposite ends with an opposite adjacent plate, each plate beingdimpled in one direction, the dimples in one plate being transverselydisplaced relative to the dimples in the adjoining plate to engage theflat surface of the adjoining plate, said dimples providing asubstantially uniform transverse laminar flow spacing between saidplates when the dimples of one plate contact the surface of a nextadjacent parallel plate, and at least one flat metal element extendingacross said package between the connected ends of said plates and Weldedto the edge of each plate to rigidly connect the plates in each package.

References Cited by the Examiner UNITED STATES PATENTS 3/1905 Shiels eta1; 165167 5/1932 Riley 1654 9/1942 Peterson 165167 X 12/1947 Karlssonet a1. 165-5 2/1954 Lundstrom 165-166 9/1954 Boyd 29-33.6 11/1959Kritzer 29-33.6 6/1960 Ramen 165166 X 7/1960 Slemmons 165166 X 6/1965Brandt 165-4 FOREIGN PATENTS 1/1957 Great Britain.

ROBERT A. OLEARY, Primary Examiner.

0 T. W. STREUEL, Assistant Examiner.

1. IN A ROTARY REGENERATIVE FLUID HEATER HAVING A STATIONARY HOUSING, ACYLINDRICAL ROTOR HAVING RADIAL PARTITIONS FORMING A PLURALITY OF SECTORSHAPED COMPARTMENTS THEREIN, REGENERATIVE HEAT EXCHANGE MATERIALPOSITIONED IN EACH OF SAID COMPARTMENTS, MEANS FOR PASSING A HEATINGFLUID AND A FLUID TO BE HEATED IN COUNTERFLOW RELATIONSHIP SEPARATELYTHROUGH SAID COMPARTMENTS CONTAINING SAID REGENERATIVE HEAT EXCHANGEMATERIAL, SAID REGENERATIVE HEAT EXCHANGE MATERIAL COMPRISING APLURALITY OF ROWS OF METALLIC PLATES ARRANGED IN STACKED ROWS, THEPLATES IN EACH ROW BEING CONNECTED BY A PERFORATE HINGE AT OPPOSITE ENDSWITH AN OPPOSITE ADJACENT PLATE, EACH PLATE BEING DIMPLED IN THE SAMEASSEMBLED DIRECTION TO PROVIDE A CLOSELY SPACED FLUID FLOW PASSAGEWAYBETWEEN ADJACENT PLATES, AND METALLIC MEANS TRANSVERSELY POSITIONEDALONG AND BETWEEN OPPOSITE CONNECTED ENDS OF AND WELDED TO EACH OF SAIDPLATES FOR RIGIDLY ATTACHING SAID PLATES IN EACH ROW OF PLATES TOMAINTAIN SAID CLOSELY SPACED RELATIONSHIP THEREBETWEEN.